1. Field of the Invention
The present invention relates to a gas separation device configured to separate a specific target gas component contained in a gas to be processed by causing an absorbing liquid to absorb the gas component, and to a packing used in the gas separation device. In particular, the present invention relates to a gas separation device useful for a carbon dioxide capturing device, a gas cleanup device for removing a hazardous gas, and a separation device for separating a specific gas component from a mixed gas, which is configured to separate or capture a target gas component, such as carbon dioxide contained in a gas to be processed such as an exhaust gas, from the gas to be processed by bringing the gas to be processed and an absorbing liquid into gas-liquid contact, and causing the absorbing liquid to absorb the target gas component, and also relates to a packing used therein.
2. Description of the Related Art
Gas separation devices to separate, remove, or capture a specific gas from a gas to be processed, such as an exhaust gas containing various types of gases, by using gas-liquid contact have heretofore been used in chemical plants, thermal power plants, and the like. For example, a carbon dioxide capturing device separates carbon dioxide by bringing an absorbing liquid, such as a monoethanol amine aqueous solution, and a carbon dioxide-containing gas into gas-liquid contact to cause the absorbing liquid to absorb the carbon dioxide, then brings the absorbing liquid after the absorption into gas-liquid contact while heating the absorbing liquid to release the carbon dioxide to a gas phase, and captures the carbon dioxide therefrom. Meanwhile, in a gas cleanup device for removing a hazardous gas component from an exhaust gas and a gas separation device for separating a specific gas component from a mixed gas, as well, absorption of a specific gas component by an absorbing liquid takes place by using gas-liquid contact. Such a device configured to conduct the gas-liquid contact includes a packing for increasing a contact area between the absorbing liquid and the gas. The device brings the absorbing liquid and the gas into the gas-liquid contact on a surface of the packing, and causes the absorbing liquid to absorb the specific gas component from the gas.
However, the absorbing liquid sometimes fails to flow evenly on the surface of the packing due to an influence of the surface tension. In this case, a liquid film of the absorbing liquid flowing on the surface of the packing converges and the contact area between the absorbing liquid and the gas decreases. The decrease in the gas-liquid contact area results in shorter detention time of the absorbing liquid on the surface of the packing even when a flow rate of the supplied absorbing liquid remains unchanged. This is because a flow velocity of the absorbing liquid increases due to the convergence of the absorbing liquid on the packing. As a consequence, there has been a problem of a reduction in the amount of absorption by way of the contact between the absorbing liquid and the gas.
In this regard, in a gas-liquid contact device described in Japanese Patent Application Laid-Open Publication No. 06-210121 (PTL 1), any one of a rough surface portion with center line average roughness equal to or above 50 μm, a porous surface portion provided with multiple drilled holes, and a mesh-like object is employed to form a gas-liquid contact surface of a packing in order to increase its gas-liquid contact area.
Meanwhile, in a gas-liquid contact device described in Japanese Patent Application Laid-Open Publication No. 06-269628 (PTL 2), a gas-liquid contact surface is formed from a material prepared by attaching a mesh-like body to a surface of a plate-like body in order to increase its gas-liquid contact area.
In the meantime, in a gas-liquid contact device described in Japanese Examined Patent Application Publication No. 07-121357 (PTL 3), a gas-liquid contact portion is formed from a gas-liquid contact unit in which three-dimensional knitted fabrics made of fibers are arranged in numerous rows along a vertical or substantially vertical direction.
Meanwhile, in a gas-liquid contact device described in Japanese Patent Application Laid-Open Publication No. 07-100324 (PTL 4), mesh-like bodies each having a sufficiently large size for covering a transverse section of a gas-liquid contact region are arranged and fixed at intervals in a traveling direction of a mixed gas. This document also states that each mesh-like body may be formed from an expanded metal plate. This literature describes that part of an injection liquid collides with surfaces of linear portions constituting a mesh of the mesh-like body and is thus splattered, whereas the rest of the injection liquid comes into contact with the mixed gas to generate an aerosol, while flowing down on side surfaces of the linear portions in such a way as to cover the side surfaces in the form of thin films.